Blender wrongly thinks I clicks a scale-cage manipulator that closest to camera - which is not the closest to mouse
This is due to Perspective view.
I seems that closer control points have larger &quot;active area&quot; around them. because reasons...?
In Orthographic view, the active area around all points is the same :).

Active areas highlighted. When cursor is in 'active area' it changes from a cross ✛ into arrows ✥

This doesn't make much sense from the UI standpoint, the 'active area' shouldn't change due to perspective. 
 It would also be nice if the 'active' point was highlighted when the cursor gets close enough. 

Possible solution:
Suggest improvements on devtalk.blender.org or rightclickselect.com and wait until they're implemented.